Relationship between foot muscle morphology and severity of pronated foot deformity and foot kinematics during gait: A preliminary study

BackgroundThe morphology of foot muscles that support the medial longitudinal arch differs between normal and pronated feet. The degree to which the difference depends on the severity of the pronated foot deformity is unclear. In the clinical setting, however, to reduce the pronated deformity, muscle-strengthening exercises are performed.Research questionDoes a relationship exist between foot muscle morphology and severity of the pronated foot deformity and foot kinematics during gait?MethodsUsing the six-item foot posture index (FPI-6), 26 study participants were assessed for their foot posture and divided into two groups of 13 participants each based on the FPI-6 score: pronated foot group (with a score of 6–9) and highly pronated foot group (with a score of 10–12). Select foot muscles were scanned with ultrasonography, and muscle thicknesses were measured. The following were the muscles of interest: abductor hallucis, flexor hallucis brevis and longus, flexor digitorum brevis and longus, and peroneus longus. Foot kinematic data during gait was collected using a three-dimensional motion capture system as a dynamic navicular drop.ResultsNo between-group differences were noted for muscle thickness and dynamic navicular drop. However, the abductor hallucis and flexor hallucis brevis thicknesses were correlated with the dynamic navicular drop, but not with the severity of the pronated foot deformity.SignificanceIn individuals with pronated foot deformity, more developed abductor hallucis and flexor hallucis brevis muscles may reduce the dynamic navicular drop that represents the degree of medial longitudinal arch deformation during the stance phase of gait.     

Classification of medial longitudinal arch kinematics during running and characteristics of foot muscle morphology in novice runners with pronated foot

BackgroundNovice runners with pronated feet are at an increased risk of running-related injuries. However, not all runners with pronated feet have increased foot pronation during running. Moreover, although foot muscle morphology is related to static foot alignment, the relationship between foot muscle morphology and foot kinematics during running remains unclear. We aimed to determine foot kinematic patterns during running among novice runners with pronated feet and the presence of a relationship between these foot kinematic patterns and foot muscle morphology.MethodsTwenty-one novice runners with pronated feet participated in this study, and data on 39 lower limbs were collected. Data on foot kinematics during running (rearfoot strike) were collected using a three-dimensional motion capture system in terms of navicular height (NH) at initial contact and dynamic navicular drop (DND). A hierarchical cluster analysis method was used to identify the optimal number of clusters based on these two foot-related kinematic variables. Following identification of the clusters, differences in cluster variables and cross-sectional areas of selected foot muscles assessed using ultrasonography in each cluster were examined. The muscles of interest included the abductor hallucis, flexor hallucis brevis and longus, flexor digitorum brevis and longus, and peroneus longus.ResultsThree subgroups were identified based on foot kinematics during running: cluster 1, lowest NH at initial contact and larger DND; cluster 2, moderate NH at initial contact and smaller DND; and cluster 3, highest NH at initial contact and larger DND. Clusters 1 and 3 had a larger abductor hallucis compared with cluster 2, and cluster 3 had a larger flexor hallucis brevis compared with cluster 2.SignificanceThese subgroups may differ in terms of resistance to and type of running-related injury. Moreover, foot kinematics during running is possibly impacted by the morphology and function of medial intrinsic foot muscles.     

The morphology of foot soft tissues is associated with running shoe type in healthy recreational runners

Objectives

To determine the differences in the morphology of foot soft tissues between runners using different types of running shoes.

The relationship between supination resistance and the kinetics and kinematics of the foot and ankle during gait

BackgroundClinical tests of foot posture and mobility are not strongly related to the dynamic kinematics of the foot during gait. These measures may be more directly related to foot and ankle kinetics. The supination resistance test (SRT) is a clinical test that may more directly measure forces acting on the weightbearing foot to provide clinicians with insight about the loading of foot structures.Research QuestionWhat is the relationship between the SRT in relaxed calcaneal stance and in single-leg-stance and the kinetics and kinematics of the foot and ankle during gait?Methods10 healthy adults between the ages of 18 and 65 were recruited to participate in this study. Three-dimensional motion analysis was performed using the Oxford Foot Model during gait. The results of the SRT were compared with peak midfoot and ankle joint moments, power generation and absorption, joint angles, and peak angular velocities and accelerations. Correlation coefficients were calculated to assess the strength of relationships between these variables and the SRT.ResultsThe SRT demonstrated significant relationships with several variables. In relaxed calcaneal stance, the SRT was inversely related to maximum midfoot pronation moments (r = −0.51), maximum midfoot plantarflexion moments (rho = −0.71), and peak midfoot power generation (r = −0.61). In single-leg-stance, the SRT was significantly related to maximum midfoot plantarflexion moments (rho = −0.55) and peak midfoot power generation (r = −0.47).SignificanceThe SRT is significantly associated to several kinetic variables that quantify midfoot loading during gait. Interventions that decrease supination resistance may have the potential to increase midfoot power generation.     

Effects of plantar intrinsic foot muscle strengthening exercise on static and dynamic foot kinematics: A pilot randomized controlled single-blind trial in individuals with pes planus

BackgroundNo reliable evidence has confirmed whether plantar intrinsic foot muscle strengthening exercises improve static and dynamic foot kinematics in individuals with pes planus.Research questionDoes the short-foot exercise affect static foot alignment and foot kinematics during gait in individuals with pes planus?MethodsThis was a randomized controlled single-blind trial involving 20 participants with pes planus who were randomly allocated to a short-foot exercise group (exercise) or a control group (controls). Exercise patients performed a progressive short-foot exercise three times per week for 8 weeks; controls received no intervention. Before and after the 8-week intervention, foot kinematics during gait, including dynamic navicular drop—the difference between navicular height at heel strike and the minimum value—and the time at which navicular height reached its minimum value were assessed, using three-dimensional motion analysis. We assessed static foot alignment by foot posture index and navicular drop test, and the thickness of the intrinsic and extrinsic foot muscles using ultrasound. All measurements were performed by one investigator (KO) blinded to the participants' allocation.ResultsAfter the 8-week intervention in the exercise group, foot posture index scores with regard to calcaneal inversion/eversion improved significantly (p < 0.05). Moreover, the time required for navicular height to reach the minimum value decreased significantly (p < 0.01).SignificanceFor individuals with pes planus, the short-foot exercise effectively corrected static foot alignment and temporal parameters of foot kinematics during gait. This temporal change, which shortens the time for navicular height to reach its minimum value, indicates an improved windlass mechanism. Therefore, short-foot exercise might effectively prevent or treat injuries related to the pes planus alignment.     

Foot muscle morphology is related to center of pressure sway and control mechanisms during single-leg standing

Maintaining balance is vitally important in everyday life. Investigating the effects of individual foot muscle morphology on balance may provide insights into neuromuscular balance control mechanisms. This study aimed to examine the correlation between the morphology of foot muscles and balance performance during single-leg standing. Twenty-eight recreational runners were recruited in this study. An ultrasound device was used to measure the thickness and cross-sectional area of three intrinsic foot muscles (abductor hallucis, flexor digitorum brevis and quadratus plantae) and peroneus muscles. Participants were required to perform 30 s of single-leg standing for three trials on a force plate, which was used to record the center of pressure (COP). The standard deviation of the amplitude and ellipse area of the COP were calculated. In addition, stabilogram diffusion analysis (SDA) was performed on COP data. Pearson correlation coefficients were computed to examine the correlation between foot muscle morphology and traditional COP parameters as well as with SDA parameters. Our results showed that larger abductor hallucis correlated to smaller COP sway, while larger peroneus muscles correlated to larger COP sway during single-leg standing. Larger abductor hallucis also benefited open-loop dynamic stability, as well as supported a more efficient transfer from open-loop to closed loop control mechanisms. These results suggest that the morphology of foot muscles plays an important role in balance performance, and that strengthening the intrinsic foot muscles may be an effective way to improve balance.     

Determination of relationship between foot arch,hindfoot, and hallux motion using Oxford foot model: Comparison between walking and running

BackgroundThe foot arch plays an important role in propulsion and shock absorption during walking and running; however, the relationship among the foot arch, metatarsal locking theory, and nature of the windlass mechanism (WM) remain unclear. Research question: What are the differences in the kinematic relationship between the foot arch, hindfoot, and hallux during walking and running?MethodsRelative angles within the foot were measured in 18 healthy men using the Oxford foot model (OFM). Data for barefoot walking at a comfortable speed and rearfoot running at 2.0 m/s were collected. Angles of the forefoot relative to the hindfoot (OFM-arch), hallux relative to the forefoot (Hallux) on the sagittal plane, and hindfoot relative to the shank (Hindfoot) on three anatomical planes were obtained. The medial longitudinal arch (MLA) angle was calculated to verify that OFM-arch can substitute the MLA angle. Each parameter was subjected to cross-correlation analysis and Wilcoxon signed-rank tests to examine the relationship with OFM-arch and compare them during walking and running.ResultOFM-arch was similar to the conventional MLA projection angle in both trials (gait: 0.79, running: 0.96 p < 0.01). Synchronization of the OFM-arch and Hallux angles was higher in running than in walking (gait: −0.09, running: −0.75 p < 0.01). Hindfoot supination was unrelated to OFM-arch. Hindfoot angle on the transverse plane exhibited a moderate relationship with OFM-arch, indicating different correlations in walking and running (gait: 0.63, running: −0.68 p < 0.01).Significance: The elevation of the foot arch due to hallux dorsiflexion differed during walking and running; hence, other factors besides WM (such as intrinsic muscles) may affect the foot arch elevation during running. The hindfoot in the frontal plane does not contribute to arch raising and foot stability during running; it features different relationships with OFM-arch during walking and running.     

Repeatability of the Oxford Foot Model: Comparison of a team of assessors with different backgrounds and no prior experience of the Oxford Foot Model

Research questionWhat is the intra- and inter-assessor error of the Oxford Foot Model (OFM) during healthy adult walking when applied by three assessors with different professional backgrounds and lower limb marker placement experience, not native to the originators of the model and with no prior clinical experience of the model?BackgroundNo previous OFM studies have examined the repeatability of more than two assessors with different backgrounds, and many of the studies have been conducted by the model originatorsMethodsThe OFM was applied to ten healthy adults on three separate occasions by three different assessors with varied professional experience and no prior involvement with the OFM (other than local training). Participants walked at self-selected speeds and intra/inter assessor error was calculated using the SEM + 95% upper confidence limit.ResultsInter-assessor errors ranged from 2.2° to 5.5° whereas intra-assessor errors fell between 1.8° and 5.5°. The error difference between assessors over the same joint angle varied from 0.4° (hindfoot/tibia dorsiflexion) to 1.5° (hindfoot/tibia inversion). The percentage of error to total range of motion varied from 11% (hindfoot/tibia dorsiflexion) to 126% (forefoot/hindfoot adduction).SignificanceBased on commonly used recommendations, the OFM is a largely repeatable tool for measuring foot kinematics during healthy adult walking when applied by assessors with no prior OFM experience, varied experience and not native to the model originators. Intra-assessor error was lower for assessors with prior anatomical knowledge and significant lower limb marker placement experience. The proportion of inter-assessor error to movement exceeded 50% of the total range of motion for four movements, notably forefoot/hindfoot adduction (126%). As such, this movement cannot be recommended as an outcome measure. Inter- and intra-assessor error, specific to each laboratory, should be considered, along with the proportion of error to range of motion when interpreting patient data.